Between breaths, the intrapleural pressure is approximately _______ mmHg less than atmospheric pressure.

Options

A. 1
B. 4
C. 8
D. 10

Answer

To solve the question regarding the intrapleural pressure between breaths, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Intrapleural Pressure**:
- Intrapleural pressure (PIP) is the pressure within the pleural cavity, which is the space between the two layers of pleura surrounding the lungs.

2. **Function of Intrapleural Pressure**:
- This pressure plays a crucial role in the mechanics of breathing. It helps in the expansion and contraction of the lungs during inhalation and exhalation.

3. **Pressure Comparison**:
- The question asks how much less the intrapleural pressure is compared to atmospheric pressure between breaths.

4. **Normal Values**:
- During normal breathing, the intrapleural pressure is typically lower than atmospheric pressure. It is known that between breaths, the intrapleural pressure is approximately 4 mmHg less than atmospheric pressure.

5. **Conclusion**:
- Therefore, the answer to the question is that between breaths, the intrapleural pressure is approximately **4 mmHg** less than atmospheric pressure.

### Final Answer:
**4 mmHg**

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